The invention is directed to reflectors for use in space.
Large reflectors have many important applications in space. Reflectors can be used, for example, to reflect sunlight onto a solar collector or to redirect a microwave power beam. Many applications require that the reflected radiation be focused onto a receiver. In a particular arrangement, the design of the reflector is determined by the ratio of the focal length, f, to the diameter of the reflector, D, required for the application.
When the receiver is far away from the reflector, high f/D ratios are usually required. Although reflectors with high f/D ratios cannot achieve the very high ratios of incident power density to focused power density that reflectors with a low f/D ratio can, reflectors with high f/D ratios can nevertheless increase power density by a factor of five to twenty. This improvement in power density can be very important when the receiver must be made small.
In many applications it is desirable to adjust the focal length of the reflector. For example, if radiation is being directed to different receivers on the ground, it is desirable to adjust the spot diameter, which varies as the focal length varies, to the particular receiver on the ground. Similarly, if radiation is being directed to a moving receiver, such as another satellite, it is desirable to maintain the spot diameter constant as the satellite moves. Unfortunately, conventional reflectors designed for space-based applications, such as the one disclosed in U.S. Pat. No. 3,326,624, issued to von Maydell on June 20, 1967, do not permit adjustment of the reflector focal length.
Because orbiting reflectors must be carried into space, the weight of a reflector is also a primary concern. Rigid reflectors generally are quite heavy and are consequently not ideally suited for space applications.